It has been supposed that the names of the letters were given to the trees, and not the names of the trees to the letters.

It is at least certain that the names of the trees and the letters coincide, and that the trees are all indigenous to Ireland.

The names of the letters in the Hebrew alphabet are also significant, but appear to be chosen indiscriminately, while there is a manifest and evidently arbitrary selection in the Celtic appellations.

The number of letters also indicate antiquity.

The ancient Irish alphabet had but sixteen characters, thus numerically corresponding with the alphabet brought into Greece by Cadmus.